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GI > Stomach 1 + 2 > Flashcards

Stomach 1 + 2 Flashcards

1
Q

What are the functions of the stomach?

A

Stores food
Starts digestion of protein
Innate defence (acidic)
Little bit of car and fat digestion

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2
Q

What is the term given to the digested food leaving the stomach entering into the duodenum?

Is it acidic or alkaline?

A

Chyme

Acidic

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3
Q

What are the 3 general parts of the stomach?

A

Fundus

Body

Antrum

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4
Q

What is the name of the point where the oesophageal tissue becomes stomach tissue? (The first part of the stomach the oesophagus leads into?)

A

Cardia

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5
Q

How does the type of cell change as it goes from the oesophageal tissue to the stomach tissue (cardia)?

A

Lower oesophagus = stratified squamous

Stomach/cardia = simple columnar

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6
Q

What are the 2 sphincters helping controlling the movement of contents through the stomach?

A

Lower oesophageal sphincter

Pyloric sphincter

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7
Q

What are sphincters made out of?

A

Smooth muscle rings

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8
Q

What is the function of the lower oesophageal sphincter?

A

Prevent reflux of stomach contents to oesophagus

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9
Q

What is the function of the pyloric sphincter?

A

Controls release of chyme into the duodenum from the stomach

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10
Q

What aids the lower oesophageal sphincter to remain closed?

A

Right crus of the diaphragm wraps around it
Acute angle

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11
Q

What part of the stomach is the Fundus?

What part of the stomach is the body?

What part of the stomach is the antrum?

A

Fundus = upper 1/3

Body = middle 1/3

Antrum = lower 1/3

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12
Q

Go to the last slide of Stomach 1 and label the stomach:

A

1 = pyloric sphincter
2 = antrum
3 = body
4 = Fundus
5 = right crus of diaphragm
6 = lower oesophageal sphincter

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13
Q

What is the function of the Rugae in the stomach?

A

They are numerous folds in the walls of the stomach which can allow the stomach to expand

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14
Q

What is receptive relaxation?

A

The peristalsis of food through the oesophagus towards the stomach leads to the reflex relexation of the proximal stomach (Fundus distends) so stomach can fill without a significant rise in pressure

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15
Q

What are the 3 layers of muscle in the stomach from innermost to outwards?

A

Oblique
Circular
Longitudinal

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16
Q

How does the thickeners of the muscle wall change as you move from proximal to distal?

A

Thinner proximal
Thicker more muscular distal

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17
Q

What is the significance of the thickness of the muscular walls of the stomach getting thicker as you go from proximal to distal?

A

Food moves faster as it descends

Meaning smaller parts can advance on but larger bits of food remain to be further digested

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18
Q

What cells line the entire surface of the stomach?

A

Surface mucus cells

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19
Q

What is the importance of surface mucus cells lining the entire surface of the stomach?

A

Produce a protective layer of mucus to protect underlying epithelia

20
Q

What are gastric pits?

A

Invaginations of the epithelium of the stomach

21
Q

What do the gastric pits lead to in the stomach?

A

Gastric glands

22
Q

What cells are found in the gastric glands?

A

Parietal cells

Chief cells

Enteroendocrine cells (like G cells)

23
Q

What is the function of parietal cells?

A

Produce stomach acid

24
Q

What is the function of chief cells?

A

Release pepsinogen = inactive form of pepsin (is a protease)

25
Q

Where are the majority of parietal cells located?

A

Body of stomach

26
Q

Where are the majority of G cells located?

What are there function?

A

Antrum

Produce Gastrin

27
Q

What are some protective mechanisms of the stomach?

A

Produce bicarbonate on the epithelial membrane to help keep layer neutral

Stomach cells regularly replaced

Prostaglandins made to support mucosal blood flow which supports the protective mucus layer

28
Q

What is the important pump that gets put on the apical membrane of a parietal cell when it needs to produce stomach acid?

A

Proton pump = H+/K+ ATPase

29
Q

What are the 2 states a parietal cell can be in?

A

Resting state

Active state

30
Q

What is a parietal cell like in the resting state?

A

Normal apical membrane

Proton pumps contained within tubulovesicles within the parietal cell

31
Q

What happens to a parietal cell when it becomes activated?

A

Apical membrane invaginates forming canaliculi+microvilli to make its SA large

Tubulovesicles fuse with canaliculi so proton pumps can pump into the stomach lumen

32
Q

What are the 3 phases of digestion?

A

Cephalic phase

Gastric phase

Intestinal phase

33
Q

What are some sensory triggers that lead to the cephalic phase of digestion/acid production?

A

Smell
Sight
Taste

34
Q

What are some gastric triggers that lead to the production of acid?

 gastric phase of digestion
A

Stretch

Presence of amino acids and small peptides

Food acts as a buffer higher pH

35
Q

What are some intestinal triggers leading to the production of HCl?

A

Chyme in duodenum/ presence of partially digested proteins

36
Q

What are the 3 receptors that can be activated to stimulate a parietal cell?

A

Gastrin receptors
Histamine receptors
Muscarinic receptors

37
Q

What simulates G cells to produce Gastrin?

A

Peptides in stomach lumen

38
Q

What type of receptors does Gastrin bind to on a parietal cell?

A

Cholecystokinin receptors

39
Q

How is acid production stimulated by vagal stimulation?

A

ACh can bind to receptors on the G cell leading to Gastrin production

ACh can bind directly to Muscarinic receptors directly on the parietal cell

40
Q

How does Histamine stimulate acid production?

A

Entero-chromaffin like cell (ECL) makes histamine which binds to H2 receptors on Parietal cell making it produce HCl

ECL also has a Muscarinic ACh receptor

41
Q

What cell inhibits acid production in the stomach?

A

D cell

42
Q

What hormone do D cells produce to inhibit acid production?

A

Somatostatin

43
Q

When do D cells secrete somatostatin?

A

When the pH in the stomach is very low (too acidic)

44
Q

What is the brief process of HCl being produced by the parietal cells?

A

Water + CO2 makes carbonic acid

Carbonic acid dissociates to H+ and HCO3- (carbonic acid catalyses)

H+ pumped out into stomach lumen across H+/K+ ATPase (apical membrane)

Bicarbonate ions pumped into venous blood antiport with Cl-

45
Q

What is the alkaline tide?

A

The venous blood leaving the stomach is more alkaline due to the anions antiporter on the basal membrane exchanging HCO3- with Cl- in the parietal cell

46
Q

What substances stimulate parietal cells to produce stomach acid?

A

Gastrin (CCK receptors)
ACh (Muscarinic receptors)
Histamine (H2 receptors)

47
Q

Look at last slide of Stomach 2, label the parietal cell

A

1 = H2O
2 = CO2
3 = carbonic anhydrase
4 = H+
5 = H+/K+ ATPase
6 = Cl-

GI (35 decks)

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